The WNV infection is primarily acquired by mosquito bites. WNV epidemic in the US started in New York in the summer of 1999, with 62 reported cases of WNV meningoencephalitis (WNVME) including 7 deaths. By 2002, the epidemic spread throughout most of the US, including 44 states and District of Columbia, with 4,156 WNV reported cases, of which, 2,741 had WNVME, and 284 deaths. WNVME occurs in 1:150 infected people. Furthermore, WNV infection presents a short asymptomatic viremic stage during which WNV can be transmitted from human to human through transfusion of viremic blood or blood components. In 2002, it was reported for the first time in US WNV infections can be acquired from infected blood components. The documented transmission of WNV through blood transfusion is of major public heath concern. Starting July 2003 nucleic acid based tests for WNV are being used to screen the blood supply under IND and to be evaluated for safety and efficacy prior to licensure. We are developing standard serum panels for WNV which could be used for validation of various WNV nucleic acid tests and to monitor the manufacturing specifications of WNV test kits. In addition we are also focusing on biological and immunological WNV studies.